In writing a syntax highlighter for Ocaml, I've dug into the code for
float literals:
let float_literal =
['0'-'9'] ['0'-'9' '_']*
('.' ['0'-'9' '_']* )?
(['e' 'E'] ['+' '-']? ['0'-'9'] ['0'-'9' '_']*)?
This matches what the reference manual says about float literals:
float-literal ::= [-] (0Ã¢â¬Â¦9) { 0Ã¢â¬Â¦9Ã¢ËÂ£ _ } [. { 0Ã¢â¬Â¦9Ã¢ËÂ£ _ }] [(eÃ¢ËÂ£ E) [+Ã¢ËÂ£ -]
(0Ã¢â¬Â¦9) { 0Ã¢â¬Â¦9Ã¢ËÂ£ _ }]
But it doesn't match some expectations I have about float literals. The
following are all float literals:
3.14 (* no problem here *)
6.022E23 (* no problem here *)
9.109e-31 (* still no problem *)
2. (* a float - blank decimal part *)
1e6 (* an integer? no, a float without a . Problem.*)
13 (* valid as a float, according to the above definition *)
Does anyone else find the last two cases kind of odd? Maybe it's not a
big deal because the 1e6 is scientific notation, which is float-y, and
the last one is always parsed as an integer, I assume because of
precedence in the lexing functions.
E.